The IBM ThinkPad X40 has the feature set, battery life, and light weight that most corporate travelers need...Since our previous X40 review (February 5), this system has gone through minor changes: It's been upgraded to a 1.2-GHz Pentium M (from 1.0 GHz) and from 802.11b to 802.11g wireless...The X40, which weighs only 3.2 pounds (with the eight-cell battery), managed...